Here's an SSCCE for your point 1:

use strict;
use warnings;

use Test::More tests => 1;

my $in = 'foo
.024. 3#  
bar';

my $want = 'foo
bar';

my $try = $in;
$try =~ s/\.024\. 3#  \n//;
is ($try, $want);
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Now it's up to you to do the same for point 2. Can you?