TTC Day Pass?

Hamiltonian here! I'm planning a weekend trip in Toronto, I'll take the train in both mornings. I'm looking into day passes for the TTC, I'm just a little confused about a few things. Anyone who knows, please provide any information you have or where I can find it as I am having a hard time finding specifics:

Where exactly can I buy a day pass? Online?

What is included in the day pass? Unlimited rides on busses, subway, street cars?

I have a presto card that I use for HSR, can I use it for TTC as well? Can I put the day pass onto my own presto account and just use my card?

Sorry if these seem silly, I'm just a little confused, thanks everyone!!