In sed, awk and grep, use .* to match zero or more of any characters. The asterisk matches zero or more of the preceding
character. Not zero or more characters. If you want to match a literal period in the LHS, then use "\.".
On the first reading, I didn't pick up on a space. It's better to put sed code in code blocks.
echo 'inp1.inTicks_vl(ch_inTicks_vl);' | sed 's/^[^ ]*\([[:digit:]]\)\.inTicks_vl[^ ]*/inTicks_v1\1/'
The ^ outside square brackets matches the beginning of a line.