The basic principle is that the trademark applied for should not be substantially altered (i.e. the physical form should not change) affecting its identity. Subject to this, changes are permissible according to rules.
A trademark registration covers names, slogans, logos, phrases, word(s), letter(s) or color(s) and similar identifiers that describe goods or services (i.e. the products).
Trademark once registered are valid for ten years. It can be renewed on expiry of this term with prescribed renewal fees.