There are two main organs:
Kidney: purify blood from toxins, and harmful chemicals and excretes them from the body in the form of urine.
Liver: inactivates and filters toxins from the bloood and removes toxic substances that have been ingested, such as food additives, harmful minerals, toxic medications, excess hormones.
the answer is slowly first, then rapidly
As covalent bonds are strong it makes the sugar phosphate backbone a stable molecule which will HV less chances for a mutation while the huydrogen bonds exist for the ease of DNA replication as they are strong in a way but weak for the replication to take place easily.