Not a full day activity, rather a two hours walk, maybe a little more if you want to see all the park. Picnics are allowed in specific places, and you can have a drink and snack in a cafe. Avoid sunny weekend afternoons, it's crowded.

Don’t know. Use the Métro! Much more environmentally friendly.

Le parc des buttes Chaumont ouvre tous les jours à 7 h et ferme à 22 h en juillet et août

Not there, but you can rent out of there and go in

Je pense que oui !

No it is not! Çan't believe those who said yes. Last year I got a Velib at the metro and rode over. Signs clearly say No Bicycles (in French)

Hi Viktor, If you're facing the lake and the Mairie de 19eme entrace is behind you, just start walking to your left around the lake and you should find it. Hope this helps! Enjoy Paris :)

Les mercredis, samedis, dimanches et jours fériés . Une séance à 16h et une a 17h ( en principe) Bon guignol.

Metro 7 to 7 bis will get you to the two stops near the parc. It's a lovely place and as one person mentioned, not many tourists particularly this time of the year. There are lots of neighborhood bistro/eateries which are quite good. Again, not many tourists. At the top of Ave. Secretan, there is a great local place with frequent live music and the food is very, very good. Hope this helps you.