First there are no new bosses or biomes yet since launch.
In fact the mistland spider webs were removed to prepare for the update to them.

If you start from scratch with your friend you will see a lot of changes to progression in terms of food. You need chain and iron to cook larger meat. Lots of food prep upgrades and some added food items.

Probably the biggest change is adding in new light armor sets along with their respective mini bosses/areas. Added food options expand you choices of HHS or SSH. Some new toys as well, nice to have a proper fist weapon.

You can tame and ride lox now.

So it won't be exactly the same game but having played before it shouldn't confuse you or anything.

That said ... not sure what kind of state cross play is in right now. Before you commit to trying to play with someone you might want to ask around how the cross play thing is working or if it is out for whatever system your friend has yet etc. Servers have been buggy with it .. it might work ok if you host or something? Not sure what you intend to do but you should ask about specifics in that regard.

Good luck, have fun!