Check out the list of emulators recommended to TAS games for each platform in the official tas videos site:
http://tasvideos.org/EmulatorResources.html

There are everything for old game platforms, like Atari, GameBoy, or MS-DOS.

For PC games on Windows only, there is a program called Hourglass: http://tasvideos.org/EmulatorResources/Hourglass.html
The site itself doesn't really recommend to use it because it is an old program without any more support. You can search further about this program.

For flash games, I search a bit myself about that, it doesn't seem like a program to TAS flash games exist.
Generally, you can use Cheat Engine to speed up or slow down some games, and you can also write automated scripts that execute button presses at exact times, but they can get out of sync really easy.
I used such a script with AutoHotKey to do TAS for one browser game (which was made in html5, not flash).

Speedrunning

tasbot compatible with flashgames/steamgames/oldgames etc

Gaming_64

Spy Fox in Hold the Mustard

Notoriety 

A Kingdom for Keflings

Bloons Adventure Time TD

PAYDAY 2 VR

Infinifactory

Minecraft (Classic)

Angry Birds Evolution

Creeper World 4

PowerWash Simulator

Foreclosed

Five Nights at Freddy's: Security Breach

Five Nights at Freddy's: Security Breach Category Extensions

DYSMANTLE

Duskers

Hypixel Zombies

Loopy Particle Simulator

Despot's Game

CrossCells

The Zachtronics Solitaire Collection

The Battle Bricks

Diner Dash

Diner Dash: Flo on the Go

Diner Dash: Flo Through Time

Speedmaster24