You're removing the submit handler from the element (see node_form(), towards the end). You should just change what you need to instead of replacing the whole thing:

$form['actions']['submit']['#value'] = t('Activate');

Also for some reason it change button class from btn-primary to btn-default. This shouldn't be happening.

That's not true, it should be happening. The btn-primary class is applied for submits with one of the following values:

• 'Confirm'
• 'Filter'
• 'Submit'
• 'Search'

You're removing the submit handler from the element (see node_form(), towards the end). You should just change what you need to instead of replacing the whole thing:

$form['actions']['submit']['#value'] = t('Activate');

Also for some reason it change button class from btn-primary to btn-default. This shouldn't be happening.

That's not true, it should be happening. The btn-primary class is applied for submits with one of the following values:

• 'Save'
• 'Confirm'
• 'Submit'
• 'Search'