Everything general was said by yaxkukmian very well. Like BRM, not jumping over stakes or that progress of others is not important. So here is my experience.
1) I am now back to NL2 after 5 years but in 2015 I was very comfortable in NL25. Then a combination of a full time job and government restrictions came so I quit. but I climbed steadily from NL2 to NL25. There is no rush. Everybody has their pace.
2) I used solid 25BI with a 5BI stop loss shot bankroll management. So I did a shot at a higher stake with 25BIs in my bankroll and went back after losing 5BIs. And repeat. 25BIs is also what you will find here in the PSGY articles as a safe BRM for NLHE.
3) Not important and I dont even remember. But I did it several times. There was some quitting every now and then. But I never got higher than NL25 and I have also never lost my BR.
4) Never and I dont recommend it either. Every stake plays a little different and there is also very huge difference between for instance NL10 and NL25. There are more regs, they play more aggressive, defend their blinds, bluff more, float etc. So take one step at a time, study slowly but steadily and you will climb up.
5) Not sure what you mean. Maybe cash out part of your bankroll to your bank account? If so, then I wouldnt do it unless you are at a stake which makes you some decent money every month. It should be a priority for you to build your bankroll and beat you current stakes.
6) Dont remember actually but I think I was stuck between NL10 and NL25 for a while. Then all of a sudden I got the grasp of it and started to beat NL25. And then I was forced to quit ♦
So good luck and if you need anything else, dont hesitate to ask.