As pointed out by others, the first three minifigures are genuine LEGO (with the second having perhaps a few custom accessories). The fourth is not a LEGO minifig. It may include some genuine LEGO elements (legs, hands, etc), but the militaristic accessories are not LEGO elements. This appears to be a custom minifig sold at one time by Modern Brick Warfare.
These came from a number of sets, including a handy "Decorated Elements" set that covered most of the printed parts from the mid-90s space theme.
However, Recon Robot appears to be the only one that contains two of the 2x2 tiles and only one of the 2x1 tiles.
Instructions can be found in a number of places, including on Let's Build It Again.
I actually managed to find the exact set while refining the question. It's set 744, released in 1980.
Here are the reasons why the research I did prior to writing the question didn't lead anywhere:
The yellow motor does not show up when searching parts on BrickLink. It's probably because on the list of set 744 parts, it has a note saying "Part colour ...
Not a great pun, but the 2016 advent calendar was:
40222-1: Christmas Build-Up
Sort-of a pun/double-meaning on LEGO being a building toy, and the set being meant to build-up to Christmas.
The 2017 version also has the same name.
3852-1: Sunblock (or Sun Block as styled on the packaging)
Here "Block" takes on 3 meaning, as part of the word "Sunblock", a pun on LEGO blocks (though I prefer to call them bricks), and a reference to the game play where you try to block your opponents from making another move.
These bags don't seem to belong to any specific LEGO set.
First, they are filled very sparsely. Normally LEGO bags are filled with more elements than that depicted here.
Secondly, in bag #3 we clearly see a Plate 6X6 W. Bow in medium lilac:
And a Right Plate 3X8 W/Angle in bright yellow:
But these two parts have never been sold in the same set. These ...
Those horses look like legit LEGO-brand horses.
White Horse with Black Eyes, White Pupils and Dark Orange Bridle Pattern: 4493c01pb04
Black Horse with Black Eyes Circled with White, Brown Bridle Pattern: 4493c01pb02
In order to be extra sure they are genuine LEGO, look for the "LEGO" stamp on the inside of the hollow studs on their back ...
It looks like the bulk of the parts are from The Chamber of Secrets (4730):
As Henrik mentioned, Sorting Hat (4701) is also present:
Jason pointed out that Dumbledore's Office (4739) is also present:
I thought it might be worth noting that these old Harry Potter sets are fairly valuable to collectors. The Chamber of Secrets alone in complete used ...
Most of this looks like it's part of the Mars Mission range - however, none of those sets contain the 2 flames, and the Minifig has both wrong colour torso (grey, instead of white), and the wrong type of helmet (he has Headgear Helmet Space instead of a Motorcyle Helment)
As for which Mars Mission set you have there, from curved Windscreen, the Technic bars ...
These are identified from left to right.
Series 18 of Lego Minifigures has that first policeman. Here is the exact minifigure.
The second one appears to be from Series 9 of Lego Minifigures. Here is the exact minifigure.
The third policeman appears to be LEGO Policeman with Riot Helmet Minifigure with a different head. The head might be Minifigure, Head ...
This game represented the LEGO Designer Sets (Make & Create) from 2003–2005, and so the majority of models are based on them (WB1 models are from the first and second waves, and WB2 the third wave). As someone who grew up with the game and the Designer Sets as a tween, and still has many of them built to this day, I believe I can answer this question ...
Left Plate W. Angle 3X12 only comes in Bright Red in 6 sets. Only 1 set also contains this piece in White.
31047-1: Propeller Plane
This set also contains:
403224: Plate 2X2 Round in Bright Yellow
4560179: Flat Tile 2X4 in Bright Red
4211440: Technic Brick 1X2, Ø4.9 in Medium Stone Grey
6083620: Cross Axle 4M With End Stop in Dark Stone Grey
So both bags ...
The red car that you mentioned is Mail Van (7820).
There are a number of other trains in the picture including:
7730 - Goods train (the locomotive doesn't seem to be visible)
7710 - Push-Along Passenger Steam Train (just the cars)
7750 - Steam Engine with Tender (pulling the cars from 7710)
7814 - Crane Wagon
7760 - Diesel Shunter Locomotive
7720 - ...
These appear in 4s in many iterations of the Imperial Shuttle, and also many of the X-wing, as well as the
MT-201 Ultra-Drill Walker and the SP Undercover Cruiser. I can't say for certain which of these sets originally contained those pieces, but this should get you closer. This list also shows sets that contain the piece in smaller quantities.
I think that is 7937 "Train Station"
I recognised the white girder piece as being in the Saturn V set
Bricklink then shows all other sets with that piece
Of the eight sets that have that piece in white, the 7937 also has two blue chairs and some grey ladders.
That looks like Container, X-Pod Barrel Section 10 x 10 x 3 1/3, which were used to store bricks for X-Pod sets.
Such container was available in Trans-Red in single set 4415, Auto Pod
And 4417, Aero Pod was the only set to use it Trans-Yellow
That's an easy one:
It's part of the Modular Buildings series in the LEGO Creator Expert line.
It's a series intended for the advanced builder, consisting of detailed buildings that click together to form a street.
These items are from different sets.
Let's begin with the most obvious - minifigure. It is a Royal Guard from Star Wars and there are couple of versions of them. Yours seems to be with arms and hands in Dark Red. Yet, there are still two version of them (depends on the type of cape you got):
Royal Guard with Dark Red Arms and Hands was part of two sets in ...
Having checked various different parts (including severely underestimating how widespread Trans-Light Blue Brick, Round 2 x 2 with Axle Hole is) I believe that this may be LEGO Friends: Pop Star Show Stage, based on Bright Light Orange Plate, Round 4 x 4 with Hole, which only appeared in 10 sets
Find for the rarest piece(s)
My usual method for identifying a set I'm not familiar with is to find the rarest part. It's not always possible to find the rarest part but I can usually guess which parts are rare given how many of them I have in my collection.
For System sets I will usually ignore unmodified bricks, plates and tiles in common colours.