New player to Genshin, which character to select for To Temper Thyself and Journey Far or is it an event I can't do yet?

You can't finish it in time to grab the constellation. You will be able to once it resets.

its taking some old character conslation even which you have to own them first. They pretty old so dont worry about it if you dont have them, you still should take some vaule stuff in it.

You can't do the constellation this round; Constellation requires 8 weeks, and only 4 out of 12 weeks remaining for this period.

When you can go for one, whichever you like/use most really. As a new player you likely won't have many options regardless. It doesn't give a character, it gives a constellation for a character you already own.