sed search string and replace the next whole line code example

Example 1: sed replace from match to end of line

Just use a similar example with using ".*" regex with sed as following:
sed 's/match_pattern.*/replacement_of_match_and_rest_of_line/' file.txt

Example 2: sed replace with newline

For substituting with newline use sed command to replace a match with a
not used char and tr command to replace that char with a newline '\n'
#For example:
echo "123." | sed -E 's/([[:digit:]]*)\./\1|next line/' | tr '|' '\n'