I'll be flying first class from Houston to Frankfurt on Lufthansa. I have a four hour layover. Then connecting to Amsterdam.
1. Will I have to pass through customs in Frankfurt?
2. Will I be able to get into the first class terminal? If so, how?
Yes, you will pass through immigration at Frankfurt.
Here is a link to an "article" about the first class terminal in Frankfurt. Perhaps this will answer your questions.
https://chrisguillebeau.com/lufthansa-first-class-terminal-at-frankfurt-airport/
I am assuming you are doing this trip on a through ticket. If you have two separate tickets the below does not apply.
- "You" never go through customs, customs is for your luggage. Your luggage will be labelled through to Amsterdam, you will not see it at Frankfurt. Customs will take place at Amsterdam. But this merely involves walking through the nothing to declare door after you have picked up your bags.
- Immigration (passport checks) will take place when you land at Frankfurt. Frankfurt to Amsterdam is an intra-Schengen flight and there will be no passport checks
- First class terminal - ask your airline.