Hi miscia76,
Re 1: There are various ways of doing this, most of which involving VBA programming and/or the use of formfields and document forms protection. See, for example, the following links, some of which use formfields and others of which use content controls:
https://www.msofficeforums.com/word/...html#post53691
https://www.msofficeforums.com/word-...html#post47254
https://www.msofficeforums.com/word-...html#post53871
https://www.msofficeforums.com/word/...html#post46903
https://www.msofficeforums.com/word/...html#post46429
https://www.msofficeforums.com/word-...html#post39327
https://www.msofficeforums.com/word-...ng-contol.html
https://www.msofficeforums.com/word/...html#post30792
Note: You should not use formfields and content controls in the same document.
Re 2: This can be achieved by VBA programming and/or by setting the password to modify option (note that the latter locks/unlocks the entire document).
Re 3: There are various ways of doing this too, some of which involving VBA programming and/or the use of formfields and document forms protection. See:
http://gregmaxey.com/word_tip_pages/repeating_data.html