Typically you should feel the heat. It should be comfortable, tolerable heat, however. The skin gets flushed and red as if you have been under the sun all day.
Yes it is safe to do as many sessions as you think needed. We typically recommend at least 5-6 sessions as a treatment (one session every week). Some people may decide to do a second round of treatment depending on their result.
The appearance of pimples could be related to irritating the skin (with injection in this case) but not necessarily a unique consequence of the filler. The red areas shown are likely bruises. Vascular occlusion causes purple discoloration, pain and usually presents early. However, you should followup with your provider if you have any concerns, experience pain or notice worsening discoloration/swelling
Botox is injected to localized area so there shouldn't be systemic effect. There is no contraindication to take antibiotics after botox injection
You can certainly do fillers to smile line. Juvederm Vollure, Juvederm Ultra, Restylane-L, Restylane Lyft or Restylane Defyne or Refyne are all good choice for this area. Given you young age, I would recommend 1 ml (one syringe). If more volume needed, you can always add to it later.
