The rule is simple, choose your method of coming back to the past.
There is nothing else special, you are an ordinary human being, on this reality, who just happened to newly possess a really special Pocket-Watch.
Considering there are different rules of time travel for each universe, i shall give you at least 4 right here. Choose well, for you cannot overcome the price of each setting.
Also, you will have to share your reason to go back to the past in the 1st place.
Limited by a margin of 10 minutes into the past, you can leap anywhere in a 5km radius.
You can also take with you into the past what you have on you.
But, because you remain in the same time-line, just make sure that you don't run into yourself or else, every leaps are cancelled for 1 entire week.
Hazardous but no Disaster.
Your entire self goes back in the past and no matter what you do, you won't break the universal timeline by being anachronical, no matter how advanced your ideas are and the profit that comes with it.
But you cannot choose at all 'when' you arrive and you won't have any tech from your present that could help and work then/there.
Only your spirit goes back to the past, installing itself in your past body.
Your actions won't destroy the universal balance, but you must take the long way home in your younger body and choose another path from here on out.
Or else you are trapped in a loop.
You can go to a specific point in time, to change something drastic in the history of human-kind, for the better, and you will be successful.
But you exchange that success for your own past-present-future timeline, disappearing into the universe, never having existed.
No cheating on the rules, you follow them or that's it.
I guess you could say that the price for not-following them, is for you to be trapped in a loop-inferno, and not ever realise it.
Every time you think something is weird, your thoughts are instantly diminished.