It is good to see you are getting an effect after using Rogaine, you can continue with Rogaine. So as you must be knowing minoxidil topical lotion is the FDA approved lotion used to control hair fall, it is used in both male and female pattern of hair fall, It is used to preserve the existing hair even it is advised post hair transplant surgery for the growth of transplanted hair.
As per the studies conducted and researchers are done on the absorption of minoxidil, it has been noted that the absorption of minoxidil in 1 hour after an application is about 30% to 40%
After 4 hours the absorption is about 60% to 75 %, and in 8 hours time, its absorption is almost 80 -90%. So ideally it is advised to keep minoxidil for 8 hours for good results or good action of the medicine.
As per your 1st question, Yes, Minoxidil is definitely safe lotion.
Here is the answer to your 2nd question, When it comes to losing the effect of minoxidil, Yes, it is possible to lose effect after tapering minoxidil. Because minoxidil helps to increase the duration of your hair to stay intact with your scalp by increasing duration of anagen phase (growth phase) & it also increases the size of a hair follicle. Therefore, definitely, you are not going to lose its effect until the time you will use Minoxidil.
Here is an answer to the 3rd query, As per your query what I understood, you need to know can I do a different hairstyle like ponytail?
Basically, minoxidil is adviced to apply on scalp not on hair strands or shaft, after application, you must have notices the amount i.e 1 ml is sufficient to cover the scalp area and within 20 to 30 minutes it gets dry without any efforts of drying it manually. So after 20-30 minutes post-application it is safe to do any hairstyle/ponytail. The hairstyle will not hamper the results of minoxidil.
So after application let the lotion get dried up on our scalp properly it will take minimum 20 to 30 minutes for the lotion to absorb on scalp then you can do whatever you like.
Even at night time application let it dry then you can go to bed , or sometimes immediately after application few people go the sleep so it may get absorbed on bed or pillow and can get in contact with your face or ears, so it may lead to excess facial hair growth , so mostly it is adviced to dry up the minioxidil properly after application then u can do your daily routine.
Also wash your hands post application of minioxidil.
Minoxidil is good if you use for your new hair growth , and there is no direct relation between use of Minoxidil and Hair Style. Regarding Ponytail due to thight ponytail patient tent to have traction alopecia, it is completely different from androgenetic alopecia. keeping pony tail everytime for longer duration will definitely lead to traction alopecia.
Here is answer for your last question, yes it is really unsafe to comb hair in ponytail, because again it will lead to more traction to your hair.