bayern ticket(Or all regional tickets)

Bayern tickets (or other Laender tickets) do. But there are also regional tickets that are train only, e.g., the Werdenfels ticket (Munich-Garmisch) or the Franken-Thueringen ticket and some others.

Actually, although the Bayern-Ticket covers all S- and U-bahn, trams, and buses in the metro transit districts (Verkehrsverbünde), like Munich MVV, and most bus lines in Bavaria (like RVO), there are a few individual bus routes that are not included.

Do regional tickets cover all forms of transport. ie train, bus and
tram for the day?

No. It does not contain long-haul trains (ICE, IC and EC), only RE and RB trains. On distances like Bamberg - Munich this can mean more than an hour difference in travel time (sometimes double travel time) and including a switch of trains which is not necessary when using an ICE.
Overview of train fleet: https://www.bahn.de/en/view/trains/index.shtml

Comparison of ticket types:
https://www.bahn.de/en/view/offers/regional/index.shtml

Info on Bayern ticket:
https://www.bahn.de/en/view/offers/regional/regional-day-ticket-for-bavaria.shtml

Although the long-distance trains ARE faster, the don't go to every town. Most stations have only regional service. There are only a few, main lines with ICE/IC/EC service. Some towns might have only one or two such trains per hour (Bamberg has four - two each direction) and often you'll still have to make at least one change of trains to get to your destination. Currently there are only four ICEs a week through Garmisch-Partenkirchen - three on Saturday, one on Sunday, none during the week.

It is just important for visitors to understand that with a Bayern-Ticket or any other regional ticket you shall not embark an ICE, IC or EC train.

The long-haul train specific network and all-train regional network maps can be seen here:
https://www.bahn.de/p/view/service/fahrplaene/streckennetz.shtml
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Just as funny side story and proof that soccer rules Germany: Deutsche Bahn has a separate website with listed stadiums of soccer clubs in first three leagues to make travel planning more easy:
https://www.bahn.de/p/view/service/fanecke/service/stadien.shtml