From rules: ''Runs use the Real Time Attack (RTA) timing convention, which means it measures the real time that has passed from start to finish, rather than in-game time. Runs may be timed with an external timer (such as WSplit), though the timer DOES NOT have to be shown on video.''
Pausing timer and game or not is not really an issue but mods may consider it as a spliced run if you're not gonna stream since it has happened a lot.
You are allowed to pause the game, but the timer has to keep running during that pause.
The GTA:SA community has been deteriorating over a long period of time. Many top runners are not currently present on the leaderboard. This issue has not been seriously addressed yet, but an attempt will be made to remedy it now.
As of this news post, the San Andreas leaderboard will function in