Is there something in particular that you're trying to figure out? If you have a specific question, it's best to just ask that question, rather than broadly asking for help.
Thanks for response dude.
Yes. Like if i am doing a full game speedrun so can i pause the game and start after sometime or i have to do it straight in one sitting ?
The vast majority of games require runs to be completed in one sitting. Some games allow you to take breaks, so be sure to check the rules for the game you're wanting to run, but that's usually only for extremely long categories (like 12-24+ hours).
I go throughed the rules in GTA 5 but still ain't clear that am I able to stop and then play again.
Generally speaking, if a run doesn't specifically allow the timer to be paused during the run for some reason (like loading screens), you can't pause the timer until the run is finished. As ShikenNuggets said, very few games will allow the runner to stop and take a break with the timer paused, so unless it specifically states as much in the category rules, you should assume it's not allowed.
Also just to mention - specific questions about category/timing rules for GTA 5 should be asked in the forum for that game. The moderators for that game are the ones who decide the rules, so they're the only people who can give you an "official" answer.