you MIGHT be able to do 4 cm.
7 days to fly, and pack and get accommodation, do doctors checks, and settle in, and prepare the things you will need after surgery.
7 days for inflammation to go down before you can start lengthening.
then you have 2 choices.
1) potentially fk yourself up with massive balarina by doing 1mm per day for 40 days..... (ps you will not be able to do this amount even if you wanted to)
2) or option 2. do 0.66mm per day for 60 days.
option 1: 7+7+40= 55 days. it could be possible that you will in 1 months time be allowed to put LON on. but I doubt any doctor will take your external frames off as you will have not enough callus.
option 2: 7+7+60= 75 days 1 month later you can get LON placed on you. no doctor will let you remove external frame straight away.
remember. after you finish lengthening you have at least 1 month before lon can be placed and external frame removed. after this 1 month it will take 1 month before you can walk without your walker and with crutches.
conclusion.............. no way in hell can you achieve this in 3 months.
75 days + 30 days (when frame is removed)(and lon placed) = 105 days 3.33 months. and even at this point in time for 4cm. you WILL NOT BE ABLE TO WALK.