What is the difference between restraint of liberty, arrest and imprisonment?

Restriction of freedom is the mildest measure. It consists in the establishment by the court of the following restrictions for the convicted person: not to leave home at a certain time of the day, not to visit certain places located within the territory of the respective municipality, not to travel outside the territory of the relevant municipality, not to visit places of mass and other events and not participate in these activities, not change the place of residence or stay, place of work and (or) study without the consent of a specialized state body.
Arrest consists in keeping the convicted person in conditions of strict isolation from society and is established for a period of one to six months. In the event that compulsory labor or correctional labor is replaced by arrest, he may be appointed for a period of less than one month. Those sentenced to arrest serve their sentences at the place of conviction in the so-called detention houses, and they must be kept under the conditions established by the PEC of the Russian Federation for those sentenced to imprisonment serving a sentence in a general regime in prison.
Deprivation of liberty consists in isolating a convicted person from society by sending him / her to a colony — a settlement, placement in an educational colony, a medical correctional institution, a correctional colony of general, strict or special regime, or to a prison. Deprivation of liberty is established for a term of two months to twenty years. However, in some cases, the total term of imprisonment can reach 25 or even 30 years (based on the cumulative sentences).