The reason for charging at 1c is when your battery is new it contains some chemicals to keep the battery in a stored state.
Charging and discharging at a low rate is best to help the chemicals break down in first 3/5 cycles. Charging at 1c will also help with the life of the battery and it will last a little longer when flying(discharging).
You can charge your battery at a higher rating as long as your battery is safe to do so but I have always charged my lipos at 1c .
There is a better write up on here with more information that will help you.
In this case 1C = 5.2Am not 1A - the capacity of the battery. e.g. a battery with a capacity of 25mA would be unlikely to be charged at 1A = 40C
“contains some chemicals to keep the battery in a stored state” This is new to me, do you have a source for this?. I know that LiPo have a preferred storage voltage - most chargers have a setting for this.
Personally I always charge well below 1C, usually at about 1/4C, although I know that many people charge at rates higher than 1C.
1C is 1x the capacity of the battery i.e
5000ma =5c = 5amps
5200ma= 5.2c = 5.2amps
0.25ma =0.25c =0.25amps this would need to be charged at 0.25a so you would need a charger that charges with a rate of 0.25c (0.25amps)
When charging go with a C rate that’s lower than your battery (it may take longer but is safer)