replace character with new line sed code example

Example 1: replace text with sed

sed -i 's/old-text/new-text/g' input.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'