Why people get sometimes a 'sensation of burning' during gels hardening but it does not happen in case of acrylic (powder and liquid)?
It depends on the time that is needed to harden certain products. Gels hardening process is faster than acrylics as they are hardened (so called 'freezing') within few seconds. Full hardening is completed after 2-3 minutes (depending on the type of gel).
Acrylics are hardened within few minutes but the whole process is completed after 28-48 hours (that is why acrylic is more prone to damage during first several hours).