Interestingly, certain types of welding are not actually that difficult to pick up, and you could get to a base competency with simple guides and fairly cheap equipment and a bit of practice on scrap.

You could absolutely build a perfectly functional bike by MIG (metal inert gas) welding mild steel. Even with little to no experience and cheap equipment.

These days, most mass produced bikes are aluminum because it’s a cheap material and the difficulties of welding it (very heat conductive, hard to get the metal at the joint to flow) are kind of irrelevant in a mass production setting. A lot of people still prefer steel bikes due to the rigidity and durability though.

Depends on the type of pine tree. Lot of the uses mentioned by others are dependent on the type. If you can identify the type, I’d try searching it.

In addition to the uses some have mentioned, some have medicinally useful compounds that can be extracted by alcohol.