The first Version of Resident Evil 3 Nemesis was 1999 for the PlayStation and only AFTER that it came out for Windows in 2000.
In the PlayStation Version you can go to GAME CONFIG => KEY CONFIG => TYPE C and then you got MANUAL AIM.

Here is the content of the translated japanese readme of the Official 1.1.0 patch by SourceNext:

/* BIOHAZARD(R) 3 PC Version 1.1.0 Patch Readme File */

*************************
About this document

This document describes the fixes and additional features in the "ver1.1.0" patch for "BIOHAZARD(R) 3 PC".
Please read this before playing after updating.

************************

[table of Contents]
1. Fixes and Additional Features
2. Contacting CAPCOM

1. Fixes and Additional Features
----------------------------------------
Fixes:
●Fixed some graphics issues.

●Fixed some system messages.

Additional Features:
●Added the ability to toggle "Door Skip" ON/OFF
By pressing "F7" on your keyboard during gameplay, you can now toggle ON/OFF the function to skip door animations when moving around the map.

●Added the ON/OFF toggle for "Auto Aim".

By pressing "F5" on your keyboard during gameplay, you can now toggle ON/OFF the "Auto Aim" feature, which automatically searches for the nearest enemy when you are in a normal attack position.

*These two additional features are active in all modes.

These two additional features are set to "OFF" by default.

*Capcom takes no responsibility for any problems that may occur when using the additional features listed above.

Please use these features at your own discretion.

2. Contact Capcom
----------------------------------------
Technical support for this product is provided by Capcom Co., Ltd.
For inquiries, please contact the support center listed below.

Capcom PC Support Center
TEL: 052-760-0335 (Weekdays 13:00-21:00)

(c)CAPCOM CO., LTD. 1999, 2006 ALL RIGHTS RESERVED.



So it should be possible to turn on the manual aim feature and make it adjustable, if it is only disabled and the developers of the 1.1.0 Patch forgot to implement that feature ...

1. There is no Option for enabling manual aim and the F5 Button which should switch aiming methods according to the readme of the SourceNext 1.1.0 Patch only displays the Option screen.

2. You are not able to assign a Control Function of the game like Cancel/Run to more than one buttons.

3. In the newest Version of the game with Rebirth Patch you can assign the Pause Button in the Configuration Tool but not in the ingame Options, so it doesnt work.

4. When start the MOD Selector or the Configuration Tool and Press Cancel or X in the upper right corner, it doesnt abort the launch of the game, it launches the game which it shouldnt.

Currently in 1.1.3 i cannot rebind movement to arrow keys, is there a workaround, is it intentional? and is there an upcoming update that we might get to allow more keybindings?

Gmail is no longer accepted for registration since it's what spambots use for email approval. All accounts using gmail have been purged, please recreate any lost account.

NOTE: this may be extended to other domains if spam bots start using those as well.

No worries, it's okay even if you posted it here since I didn't think of making a DC2 section. Anyways, bug's in the list of things I fixed for v1.0.1, bug report appreciated!