PHP warnings and fatal errors

I have quite a few errors, that have been happening that I was made aware of only now. I need help in fixing them. I am fairly new to all this, so please explain all the techie terms.

1.)

21-Feb-2013 07:31:41 PHP Warning:  require(includes/templates/template_default/templates/tpl_about_us_default.php) [<a href='function.require'>function.require</a>]: failed to open stream: No such file or directory in /includes/templates/template_default/common/tpl_main_page.php on line 122
[21-Feb-2013 07:31:41] PHP Warning:  require(includes/templates/template_default/templates/tpl_about_us_default.php) [<a href='function.require'>function.require</a>]: failed to open stream: No such file or directory in /includes/templates/template_default/common/tpl_main_page.php on line 122
[21-Feb-2013 07:31:41] PHP Fatal error:  require() [<a href='function.require'>function.require</a>]: Failed opening required 'includes/templates/template_default/templates/tpl_about_us_default.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /includes/templates/template_default/common/tpl_main_page.php on line 122

2.)

[01-Mar-2013 10:40:09] PHP Parse error:  syntax error, unexpected T_STRING in includes/languages/english/customtemplate/header.php on line 33

3.)

[03-Feb-2014 10:05:00] PHP Fatal error:  1317:Query execution was interrupted :: select configuration_key as cfgkey, configuration_value as cfgvalue
                          from zencart_product_type_layout in public_html/includes/classes/db/mysql/query_factory.php on line 120

4.)

[31-Jul-2015 18:41:09] PHP Parse error:  syntax error, unexpected $end in /includes/classes/shipping.php on line 185

5.)

[16-Nov-2015 11:31:11] PHP Warning:  constant() [<a href='function.constant'>function.constant</a>]: Couldn't find constant MODULE_ORDER_TOTAL_INSURANCE_ZONE_3 in includes/modules/order_total/ot_insurance.php on line 43

6.)

[24-Nov-2015 03:59:36] PHP Fatal error:  1054:Unknown column 'show_box_min_width' in 'field list' :: select layout_box_name, show_box_min_width from zencart_layout_boxes where layout_box_location = 0 and layout_box_status= '1' and layout_template ='responsive_all_business' order by layout_box_sort_order in includes/classes/db/mysql/query_factory.php on line 120

7.)

[30-Jul-2015 16:57:39] PHP Fatal error:  1062:Duplicate entry 'FEAC_VERSION' for key 'unq_config_key_zen' :: INSERT INTO zencart_configuration (configuration_title, configuration_key, configuration_value, configuration_description, configuration_group_id, sort_order, last_modified, date_added, use_function, set_function) VALUES
                    ('Version', 'FEAC_VERSION', '0.0.0', 'Version installed:', 32, 0, NOW(), NOW(), NULL, NULL); in includes/classes/db/mysql/query_factory.php on line 120

Welcome -
Please provide the additional information in posting tips at the top when you reply

includes/templates/template_default/templates/tpl_about_us_default.php
It looks as though you might have edited the tpl_main_page.php due to the fact that there is a "require" for the about us page and that is not p[art of the stock code

First things first, want to address the most recent one(s) first, then consider the older ones. If all of the above are repetatively occurring, then want to address the ones that are causing a noticeable problem first.

All that said, it looks like item 6 is the first I would evaluate. It looks like possibly a new template was either installed or attempted to be modified. When was the responsive template responsive_all_business added to the site and have there been any issues in customizing it since?

As to the remaining items, if they are not recurring then they are just events of the past, though ideally they be reviewed to know/understand what things happened to the store in the past... But otherwise, they would be for learning but of little value for "problem" resolution.

I did not even notice the dates...