There is no age limit. Takes 8 months to 2 years. Clear aligners are totally invisible and many brands are available .hidden braces or lingual braces are also almost invisible

At 30 years you can put braces . The Ortho treatment last from 8-30 months depending on your teeth . Yes lingual braces and clear aligners are like hidden braces A plus point with clear aligners is that you can remove and wear it and does not require monthly visit to the dentist . Also there are no diet restrictions with clear aligners

can u send me your opg..i wil be able t guide u better

At the age of 30 you can definitely go for braces treatment, provided you don't have any gum disease,duration of treatment will depend on what is the requirement.If just want some spacing between teeth to be corrected, might get over faster, if your teeth are too much forwardly placed or very crooked then some teeth need to be removed to straighten out your teeth,which Will take longer.Generally between 1-2 yrs. Yes ,there are options like clear aligners or lingual braces where the braces won't be visible, you can consult an orthodontist who can guide you as to which option is the best for you.