Multi-company setup and help with Groups

Multi-company setup and help with Groups

Hi,

I'm currently evaluating the suitability of Zoho for our business needs.   Once I'm satisfied Zoho will suit our needs, I'll make use of all of the other Zoho modules (CRM, etc).

Multi-Company setup
I'm looking to use 1 account to to maintain Mail/Calendar/Tasks for 3 different companies plus my personal stuff.
We have several groups of contacts that are common to the 3 companies as well as me personally.

I have set up 4 organizational groups, 1 for each company and one for my personal stuff.

I have created a master list of contacts in my personal Contacts account, each of which has been categorised, many contacts having multiple categories.  These are not in any Organisational Group at present, just in 'My Contacts'

How do I allocate the individual contacts to their relevant groups based on their category?

This is what I have tried:
1) Export all contacts from 'My Contacts'
2) Imported to each Group

I have several issues with this:
a) the categories are lost on import
b) if I subsequently add a contact to any of the groups, if this new contact belongs to multiple groups, I have to add to each group manually (as opposed to adding in one central place then selecting the groups you want the contact to propogate to.
c) There is no means of allocating a category (and therefore filtering) when the contact is shared in a group. Category selection is only available for 'My Contacts' and not 'Shared Contacts' of any group under the 'Views' tab.

How can I maintain a central Contact list where members of the Group for each company have access to only the contacts in that group (plus any local Personal Contacts), without adding duplicate entries of the same contact across the various groups?

I have looked at maintaining 4 seperate accounts (1 for each company plus a personal one) but whilst this removes the issue with categories it means multiple logins, I have problems with only being able to allocate a person to one Zoho account and it doesn't solve the issue of maintaining multiple common contact entries across all of the accounts
How do you filter for multiple categories in 'My Contacts'?
I am about to evaluate Zoho CRM.  Am I able to overcome the above issues with Zoho CRM? If so, how??

Help with Groups
Are there any further help files other than the ones in https://zohomail.wiki.zoho.com/ which explain how Organizational and Personal groups work?
 

The documentation on groups and how to use them is virtually non-exeisting in the Mail wiki.  There is very little in there which explains:
How to use groups
Difference between Personal and Organizational groups
Process of 'inviting' and 'adding' members
Difference between adding members of the organisation and non-orgnaisational members (what they have access to etc);
How the chat facility works (in Mail)

Am I correct in saying that when on your 'personal' (ie not control panel) page, if you 'Invite to Group', this refers to a Personal Group (not an Organizational Group) whereas when in the control panel you 'add' members to the Organisational Groups? 

If you invite a person to an organizational group who is not a member of the organisation (eg an external supplier), do they still have access to the Group contact list?

Regards
Keith